"Occasional" 240v

[PaulRainbow]

It would make more sense if the AC ground wire was connected to a metal object in the water giving direct conductivity to the sea, then if there was any leakage in the AC line into the water the RCD would trip.

If the DC was not isolated or insulated it would not matter if it was also connected to the DC negative

The DC negative as such is not relevant its what the DC negative is also connected to like the sea through the engine/stern gear, so why not just connect the AC earth direct to the sea and ignore the DC negative so it not directly relevant

This would then apply to all hull types it the AC earth connection to the sea that important in all cases.

For a shore power installation, i'd agree, if one wanted to follow the ISO, which i'm not entirely sure i agree with.

For the inverter though, simply connecting the AC ground to the DC negative is enough. There are some inverters where the AC ground is internally connected to the case, the case then has to be connected to DC negative. Some have the AC negative connected to the case, which is then connected to DC negative. Some can have all of the connections made internally.

Then there are of course centre tap inverters, these are less common and usually small, these obviously don't have the ground wire connected to DC negative, but will still trip an RCD.

 

[solent clown]

A. Which RS inverter please ?
B. No instructions ?
C. Is there a manufacturers name on it ?

Paul, it's an old one I have had kicking about for donkeys years, i use it normally for emergency running a grinder in a field/barn, airfield, wherever I am coaxing a piece of long forgotten and abandoned machinery back to life or gutting it's donor parts to save another. It is an industrial steel cased cuboid. I shall attempt to decipher the runes on the morrow, and furnish you with more information.
To recap, my plan was to run it on it's own battery with a manual switch to charge it as and when I wish from the engine.
In the absence of any other contrary advice on here my plan was to use a small consumer unit, and run the RCD neutral to the earth bonding point on the inverter chassis. I was also going to bond the earths, and run a wire down to a keel bolt for good measure. probably not needed, but what the heck

 

[PaulRainbow]

Paul, it's an old one I have had kicking about for donkeys years, i use it normally for emergency running a grinder in a field/barn, airfield, wherever I am coaxing a piece of long forgotten and abandoned machinery back to life or gutting it's donor parts to save another. It is an industrial steel cased cuboid. I shall attempt to decipher the runes on the morrow, and furnish you with more information.
To recap, my plan was to run it on it's own battery with a manual switch to charge it as and when I wish from the engine.
In the absence of any other contrary advice on here my plan was to use a small consumer unit, and run the RCD neutral to the earth bonding point on the inverter chassis. I was also going to bond the earths, and run a wire down to a keel bolt for good measure. probably not needed, but what the heck

Would be useful to carry out a couple of tests on the inverter to see how it's internally connected, but in essence it's not going to be too different from fitting in a vehicle. It's worth remembering, in a vehicle there is no ground (as in earth stake in the dirt ground), vehicle inverters are usually "grounded" to the DC negative, or the bodywork (which is the same thing, of course).

I'd be interested in the results of a quick test with a 40w 240v light bulb, if you have the time. I'll PM you.

 

[solent clown]

Would be useful to carry out a couple of tests on the inverter to see how it's internally connected, but in essence it's not going to be too different from fitting in a vehicle. It's worth remembering, in a vehicle there is no ground (as in earth stake in the dirt ground), vehicle inverters are usually "grounded" to the DC negative, or the bodywork (which is the same thing, of course).

I'd be interested in the results of a quick test with a 40w 240v light bulb, if you have the time. I'll PM you.

yes Paul, I hear you there about the ground, But in use for expeditions, it is good practice to drive a ground pole into the earth when camped. Doing this in a boat is new to me, hence a little paranoia. Feel free to Pm me mate

 

[matthewriches]

Part 2...

And Part 3 as camera died...

 

[matthewriches]

No major secret in testing them. Same as you would do a genny. With a filament bulb do the following. You can also use a meter at the same time to see exact readings.

Best case...
Live to neutral = 230v full brightness
Live to earth = 230v full brightness
Neutral to earth = 0v off

Leave it... it’s ok. Already bonded.


Ok case...
Live to neutral = 230v full brightness
Live to earth = 0v off
Neutral to earth = 0v off

Probably ok to bond neutral to earth but do so at your own risk. The same amount of kick comes out of these sockets as a wall socket! Just because it is 12v, it doesn’t make it “safe”


Something like...
Live to neutral = 230v full brightness
Live to earth = 115v half brightness
Neutral to earth = 115v half brightness

Should be centre tapped so just leave it as it is. You don’t want a 1/2 short to earth.



Anything else then investigations start but if this was something I was doing o my own vessel, I’d be wanting off the shelf functionality with no end user modification necessary.

Just today I have spent an afternoon with an insurance assessor determining the cause of a fire onboard a river cruiser. Nightmare!

 

[PaulRainbow]

No major secret in testing them. Same as you would do a genny. With a filament bulb do the following. You can also use a meter at the same time to see exact readings.

Best case...
Live to neutral = 230v full brightness
Live to earth = 230v full brightness
Neutral to earth = 0v off

Leave it... it’s ok. Already bonded.

AC neg and AC ground are bonded, but there's still no connection to a "ground" or to the boats hull (steel boat), ground plate or DC neg, etc. If AC positive contacts the metal case of a piece of equipment it will create a short and trip the MCB. I don't see how the RCD can work ?

Ok case...
Live to neutral = 230v full brightness
Live to earth = 0v off
Neutral to earth = 0v off

Probably ok to bond neutral to earth but do so at your own risk. The same amount of kick comes out of these sockets as a wall socket! Just because it is 12v, it doesn’t make it “safe”

It's an "ok case" if you're proving the inverter isn't centre tapped, not so much OK if you want the MCB or RCD to work. Something has to be bonded somewhere or neither will work ?

Something like...
Live to neutral = 230v full brightness
Live to earth = 115v half brightness
Neutral to earth = 115v half brightness

Should be centre tapped so just leave it as it is. You don’t want a 1/2 short to earth.

I agree !

Your findings with the Durite inverter are rather puzzling What do the installation instructions say ? I've not been able to locate any online.

Thanks for taking the time to put the tests together :encouragement:

 

[PaulRainbow]

Having never fitted a Durite inverter and not being able to find online fitting instructions, i contacted Durite.

Connect the inverter case ground terminal to the chassis ground when installing in a vehicle, the vessel’s grounding system in a boat or to earth in a fixed location. The case ground terminal is
connected to the ground terminal in the ac outlet socket.

 

[matthewriches]

Already spoken to them with a simple open question and their answer to me was that they do not have any technical information available on fitting to marine applications.

So a nearly new Durite inverter as per my video acts the way it does when AC earth connected to DC negative....



More have arrived so when I get a chance, I'll run them up and try not to blow them up!!

Having never fitted a Durite inverter and not being able to find online fitting instructions, i contacted Durite.

 

[PaulRainbow]

Already spoken to them with a simple open question and their answer to me was that they do not have any technical information available on fitting to marine applications.

Odd, the quote i posted is taken from their fitting instructions, which includes "the vessel’s grounding system in a boat"

So a nearly new Durite inverter as per my video acts the way it does when AC earth connected to DC negative....

Which is also odd, because the fitting instructions state the AC earth is connected to the case and the case has to be connected to "the vessel’s grounding system", which invariably includes the DC negative.

More have arrived so when I get a chance, I'll run them up and try not to blow them up!!

Be sure to post the videos, especially if they do blow up :

 

[VicS]

Having never fitted a Durite inverter and not being able to find online fitting instructions, i contacted Durite.

Connect the inverter case ground terminal to the chassis ground when installing in a vehicle, the vessel’s grounding system in a boat or to earth in a fixed location. The case ground terminal is
connected to the ground terminal in the ac outlet socket.

So it seems that the output is floating, ie no neutral just two equal conductors , and that if connected as advised by Durite an RCD will be serving no useful purpose, at least until one fault has "earthed" one of the conductors.

Perhaps there are capacitors between the two output conductors and the case ground terminal. Would this explain the apparent centretap that mathewriches' initial voltage measurements sort of suggested but did not convincingly prove?

 

[BabaYaga]

the AC earth is connected to the case and the case has to be connected to "the vessel’s grounding system", which invariably includes the DC negative.

...unless of course the DC system is of the fully insulated type, in which case connecting to DC negative is pointless, at best. (As already covered in post #55 of this thread )

 

[PaulRainbow]

...unless of course the DC system is of the fully insulated type, in which case connecting to DC negative is pointless, at best. (As already covered in post #55 of this thread )

Yes, i'm aware of that. I think we've already established that "grounding system" means different things with different boats. Could be a metal hull, could be a ground plate, an anode or the DC negative if that is part of the bonding circuit.

 

[PaulRainbow]

So it seems that the output is floating, ie no neutral just two equal conductors , and that if connected as advised by Durite an RCD will be serving no useful purpose, at least until one fault has "earthed" one of the conductors.

Perhaps there are capacitors between the two output conductors and the case ground terminal. Would this explain the apparent centretap that mathewriches' initial voltage measurements sort of suggested but did not convincingly prove?

Further communications with Durite and i'm told the inverters are in fact centre tapped, although they referred to them as centre tied. I'm told that if a fault occurs the inverter will shut down faster than an RCD.

 

[matthewriches]

This thread is a comedy of errors really :disgust: lol

 

[solent clown]

This thread is a comedy of errors really :disgust: lol

yes, and let's keep them all in the online, and R + D arena in the hands of experts :encouragement: You chaps carry on, thank you on my behalf and any others who may come across this later, and when I get a minute this weekend I will investigate our own ancient inverter and report back . For me it has all been about being sure an RCD would work. Maybe too cautious for our use, but that is my goal.

 

[<152587>]

Source of amazement as how a question on a forum can induce what I would term bullying, disrespect for other peoples knowledge, downright rudeness and the use of capital letters in a post, presumably to interpret shouting. Forum "experts" should re-read their inputs maybe a week later after they have calmed down and maybe realise the way they promote themselves to the wider audience. Some of you do yourselves no favours, you know who you are.

 

[solent clown]

Source of amazement as how a question on a forum can induce what I would term bullying, disrespect for other peoples knowledge, downright rudeness and the use of capital letters in a post, presumably to interpret shouting. Forum "experts" should re-read their inputs maybe a week later after they have calmed down and maybe realise the way they promote themselves to the wider audience. Some of you do yourselves no favours, you know who you are.

I know what you mean generally about forums, but I think in the case of this thread all the protagonists are big enough and ugly enough to disagree without it turning in to a bun fight... Ever the optimist, perhaps, but so far so good.

 

[Moderator]

It is clear this thread shows the myriad difficulties faced by perfectly competent electricians and techies when faced with systems and equipment which is neither fully nor accurately documented.

The willingness of specialists to try out Plan A, then Plans B, C, D... and explain openly their thinking step by step is an example of the forums supporting the boating community at its best, and advancing community knowledge.

Please do not stir the pot by making disparaging remarks and discouraging people from contributing. You know who you are.

 

[VicS]

yes, and let's keep them all in the online, and R + D arena in the hands of experts :encouragement: You chaps carry on, thank you on my behalf and any others who may come across this later, and when I get a minute this weekend I will investigate our own ancient inverter and report back . For me it has all been about being sure an RCD would work. Maybe too cautious for our use, but that is my goal.

I am sure you must be as confused as I am about the earthing arrangements of inverters and the use of an RCD with them.

I think these two paragraphs from one of Stirling's instruction manuals may shed some light on the matter.

Inverters tend to come in 2 different versions.

Centre tapped Earth ( fig 3 ) where, in effect, you have no real live and neutral but 2 lives and no neutral . You have 110V on either side of the
earth terminal making 220V across the two pins (live to “neutral”) but both pins are actually live. This is the most common and is default on this
range of inverters products . If no RCD is used this would probably be the best / safety option. The worst case event you will only get a 110V shock,
however, it is recommended that a RCD be used on all inverters but we recognise that a lot of people do not use RCDs* especially with smaller
units, so,alough ilegal to do so, we can only give the best advice to our customer base who adopt poor practices. It is Sterling Power Products actual
advice that all inverters should be used in conjunction with a RCD for ultimate safety and to comply with electrical installation codes. If you do fit a
RCD (as you are suppose to) a centre tapped inverter would be your safest option, but it will not operate a RCD safely it is, therefore, vital that if
you want to use a RCD in line with the AC output then the inverter unit must be converted from Centre tapped earth to Neutral earth bonded,
failure to do so will render the RCD ineffective.

Neutral Earth bonded ( fig 4 ), this is where the neutral is tied to the earth terminal giving 230V across the live and neutral ( more in keeping with
the actual mains configuration ) but also 230V from live to earth. This allows a RCD to safely operate and confirm with hard wire installation
requirements on vehicles and boats etc.​

The centre tapped earth type referred to in the first paragraph is easily converted to neutral earth bonding. The manual describes how to do it and the necessary link is supplied